The spatial distribution of fishes in relation to habitat in North Temperate Lakes
The distribution of littoral fishes in eutrophic Lake Mendota was related to the abundance and spatial heterogeneity of submerged vegetation. Two littoral assemblages were discerned. A depauperate and distinct assemblage, characterized by rock bass and smallmouth bass, was associated with the absence of vegetation. No strong segregation of fishes among macrophyte habitats was evidenced. Bluegill, black crappie, and yellow perch dominated the catch and distributed unevenly throughout the vegetated littoral. Age-0 fish were more abundant and species-rich in the nearshore shallows than farther offshore. Adults were less aggregated and less closely associated with macrophyte habitat than were age-0 fishes. Fish species differed in their response to attributes of the macrophytes. Catch abundance of age-D bluegills correlated with species richness and was higher at sites where vegetation was abundant and patchy. Higher abundances of yellow perch occurred with more abundant and heterogeneous vegetation. There was no strong effect of Eurasian milfoil on the distribution of fishes. Increased patchiness due to the decline of this exotic or to mechanical harvesting, and restoration of species-rich macrophyte communities, may enhance the abundance and diversity of fish. We evaluated analytical approaches to discriminating littoral fish assemblages with catch data from seines, fyke nets and gill nets. Fyke nets best discerned differences among littoral assemblages. Gill nets did not differentiate among sites. Age-0 bluegills and black crappies caught in the fyke nets were the strongest discriminators. Analysis of absolute abundance data detected differences among sites; analysis of presence-absence and rank abundance data did not. We reviewed a broad range of studies of north temperate lake fish communities, focusing on the role of habitat heterogeneity in structuring communities. In community analysis, patterns in the distribution of species are related to environmental and biotic factors. The structure of the community represents the response of the community to past and current socioenvironmental factors, both locally and regionally. The processes that structure and maintain communities, and their relative importance, differ among communities and vary with scale. Through comprehensive analysis of fish community structure and dynamics, fisheries biologists can better understand the systems they study and manage.